linux-kernel - Re: [PATCH] [media] uvcvideo: Fix clock param realtime setting

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Message-ID: <16236471.uFSjvbT2di@avalon>
Date:	Fri, 28 Mar 2014 17:20:13 +0100
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Olivier Langlois <olivier@...llion01.com>
Cc:	m.chehab@...sung.com, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, Stable <stable@...r.kernel.org>
Subject: Re: [PATCH] [media] uvcvideo: Fix clock param realtime setting

Hi Olivier,

Thank you for the patch.

On Friday 28 March 2014 01:42:38 Olivier Langlois wrote:
> timestamps in v4l2 buffers returned to userspace are updated in
> uvc_video_clock_update() which uses timestamps fetched from
> uvc_video_clock_decode() by calling unconditionally ktime_get_ts().
> 
> Hence setting the module clock param to realtime have no effect
> before this patch.
> 
> This has been tested with ffmpeg:
> 
> ffmpeg -y -f v4l2 -input_format yuyv422 -video_size 640x480 -framerate 30 -i
> /dev/video0 \ -f alsa -acodec pcm_s16le -ar 16000 -ac 1 -i default \
>  -c:v libx264 -preset ultrafast \
>  -c:a libfdk_aac \
>  out.mkv
> 
> and inspecting the v4l2 input starting timestamp.
> 
> Signed-off-by: Olivier Langlois <olivier@...llion01.com>
> Cc: Stable <stable@...r.kernel.org>

Before applying this, I'm curious, do you have a use case for realtime time 
stamps ?

> ---
>  drivers/media/usb/uvc/uvc_video.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c
> b/drivers/media/usb/uvc/uvc_video.c index 898c208..c79db33 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -361,6 +361,14 @@ static int uvc_commit_video(struct uvc_streaming
> *stream, * Clocks and timestamps
>   */
> 
> +static inline void uvc_video_get_ts(struct timespec *ts)
> +{
> +	if (uvc_clock_param == CLOCK_MONOTONIC)
> +		ktime_get_ts(ts);
> +	else
> +		ktime_get_real_ts(ts);
> +}
> +
>  static void
>  uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer
> *buf, const __u8 *data, int len)
> @@ -420,7 +428,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream,
> struct uvc_buffer *buf, stream->clock.last_sof = dev_sof;
> 
>  	host_sof = usb_get_current_frame_number(stream->dev->udev);
> -	ktime_get_ts(&ts);
> +	uvc_video_get_ts(&ts);
> 
>  	/* The UVC specification allows device implementations that can't obtain
>  	 * the USB frame number to keep their own frame counters as long as they
> @@ -1011,10 +1019,7 @@ static int uvc_video_decode_start(struct
> uvc_streaming *stream,
> 			return -ENODATA;
>  		}
> 
> -		if (uvc_clock_param == CLOCK_MONOTONIC)
> -			ktime_get_ts(&ts);
> -		else
> -			ktime_get_real_ts(&ts);
> +		uvc_video_get_ts(&ts);
> 
>  		buf->buf.v4l2_buf.sequence = stream->sequence;
>  		buf->buf.v4l2_buf.timestamp.tv_sec = ts.tv_sec;

-- 
Regards,

Laurent Pinchart

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